1. Field of the Invention
This invention relates to a method and apparatus to permit attachment of tufts of individual bristles to toothbrushes with resiliently flexible, angled or curved heads and to then permit the trimming of such tufts of individual bristles to a desired length--or lengths in the case of brushes with multi-level tufts--and to then permit the rounding of the free ends of the individual bristles in each such tuft, which method and apparatus require only the modification of conventional toothbrush tufting and trimming machines and methods.
In particular, the present invention discloses novel means to deform and hold securely the head of a resiliently flexible, angled toothbrush at the tufting apparatus in order align the longitudinal axes of the tuft holes in a direction generally parallel to the direction of travel of the bristle insertion tool and to deform and hold securely the head of such a brush at the trimming and end rounding stations of a toothbrush finishing machine so that conventional tufting, trimming and end rounding machines and methods can be used in the manufacture of such brushes by the modifications according to the present invention. In many instances, the deformation results in the flattening of the head. Following completion of the tufting and then the finishing operations, when the brush is removed from the clamping means, the head returns to its original configuration.
2. Description of the Prior Art
Toothbrushes with curved or angled bristle tip configurations that offer improved access to hard-to-reach areas such as the lingual surfaces of the front teeth, and behind the rear molars, placing more bristles in contact with the outer surfaces of the front teeth are well known in the art. However, many current brushes which have rigidly mounted bristles and a rigid curved or angled bristle surface exhibit an inherent disadvantage when brushing both flat as well as concave tooth surfaces because placing a curved or angled bristle surface on flat tooth surfaces results in fewer bristles making contact with the teeth. These fewer bristles must support the brushing forces applied through the handle, which will result in premature splaying of the bristles. Some toothbrushes have a "power tip" configuration (elongated rigidly mounted tip bristles) which are claimed to have improved access benefits. Such brushes are illustrated in WO 94/09678; GB 304,459; U.S. Pat. No. 1,639,880, and U.S. Pat. No. 4,800,608, the teachings of which are incorporated herein in their entirety. Thus, while fixed angled or curved heads offer improved access to difficult-to-reach areas, because of their shortcomings with respect the brushing of flat tooth surfaces, it would be desirable to have an angled or curved brush head that flexes back to a flattened position when the brush is subjected to typical brushing forces.
Toothbrushes having heads with fixed angles or curves present another problem as well in their manufacture, particularly with respect to the attachment of tufts and the finishing thereof. Conventional toothbrush tufting machines operate in two axes, but the curved or angled section of the head does not lie within the area of operation of the tufting tool. Therefore, it becomes necessary to rotate the brush to a new position in order to bring the bristle-receiving face into the correct position in which the tufting tool can insert the bristles. While modern machines exist that can tuft brushes with other than flat bristle-receiving surfaces because both the brush and tufting tool can rotate, such machines are expensive. It is also known that conventional tuft drivers can insert bristles in an angled tuft hole provided that the angle is limited, generally to 6 degrees or less, by use of an angled tuft pin that is inserted straight and the driver, made of a thin piece of flexible metal, simply bends as the bristles follow the direction of the tuft hole. Nevertheless, it is desirable to have the capability of attaching tufts of bristles to toothbrushes with flexible angled or curved heads and of trimming such tufts of bristles to a desired length--or lengths in the case of brushes with multi-level tufts--and of then rounding the free ends of the bristles, which requires only the modification of conventional toothbrush tufting and trimming machines and methods.
Toothbrushes that include heads having pivoting or articulated sections joined together in a variety of constructions, such as by hinged articulated sections, are well known in the art.
For example, WO 92/17093, the teachings of which are incorporated herein in their entirety, discloses a toothbrush in which the head is divided by one or more hinge-forming grooves in the side of the head opposite to the bristle-bearing side into at least two segments that are flexibly and resiliently linked to each other and/or to the toothbrush handle. The head of such brush is flat, however.
WO 96/02165, the teachings of which are incorporated herein in their entirety, discloses toothbrushes with resilient, flexible heads, certain embodiments of which are similar to those shown in WO 92/17093. One embodiment has a curved head in the unstressed position and is formed by an elastomer-covered thin extension of the handle material. However, the specification merely states that the "Cutting and end-rounding of the bristles can be done using any of the methods commonly known in the art." No specific information is given, and the other embodiments disclose brushes with flat heads. WO 97/07707, the teachings of which are incorporated herein in their entirety, discloses a toothbrush in which the flexibility of the head is concentrated in the tip of the head, the head being angled at the tip. While this publication discloses that the hard plastic skeleton is made by injection molding, wherein the bristle face is substantially flat, and the tip region is subsequently folded to a desired angle with the base region, following which the elastomer is injected at a link region between the two segments, it simply teaches that the bristle are ". . . inserted by a conventional process . . . ." Again, no specific method or apparatus is disclosed to tuft, trim and end round the bristles of a flexible headed toothbrush, wherein at least a portion of the head may be at an angle with respect to the balance of the head.
Co-pending U.S. application Ser. No. 08/762,783, U.S. Pat. No. 5,758,383, the teachings of which are incorporated herein in their entirety, discloses a toothbrush having a resiliently flexible, angled head, but no specific teaching is present with respect to the tufting, trimming and end rounding operations.
EP 0 078 569 and U.S. Pat. No. 5,165,761, the teachings of which are incorporated herein in their entirety, each disclose the end rounding of toothbrushes with multi-level bristles, but the bristle faces are flat.
Toothbrushes having flexible angled or curved heads do not fit well into existing clamps of conventional tufting and finishing machines. The bent or curved head can slip out of, or be folded inwardly in the case of segmented brush heads, by typical clamps.